We wish to identify a large number of skeletal muscle cell surface proteins, using monoclonal antibodies to define the approximate number and distribution of each protein in the sarcolemma of muscle cells in tissue culture and in vivo. Some physico-chemical characterization of these cell surface proteins will be done and the metabolic turnover rates of these molecules will be measured. The first goal of this research is to determine whether cell surface proteins have unique turnover rates and whether turnover rate correlates with specific interactions with other cell components. The second goal is to determine which molecule subserves which function in the plasma membrane. The third goal is to identify molecules which become components of neuromuscular junctions or which are other-wise under neural influence in vivo. The larger goal is to know the skeletal muscle plasma membrane and basement membrane in quantitative molecular and functional terms and to know the structure and mechanisms of biogenesis of the synaptic connections between nerve and muscle.